Mixed Exposure Options

Motivation:

Exposing patterns with simpler characteristics can be easily optimized in one exposure. Exposing patterns with complex or mixed characteristics can be challenging and may require breaking up into multiple exposures. Take advantage of multiple options for fracturing, sorting or field control within a single exposure file and achieve optimum results for complex layouts. BEAMER has the ability within the export module using the “Cell To Field” option to combine multiple fractures with various options into one exposure file. As an example we apply this technique to a layout incorporating both horizontal and vertical gratings spanning multiple deflection fields, plus another example of mixing floating and overlapping fields is included in the downloadable PDF file.

Solution:

The vertical and horizontal grating sections are first separated with individual Extracts. The Export modules are next with Field Ordering options in the advanced tab selected for vertical raster for the vertical gratings, and horizontal raster for the horizontal gratings. Next the exported tool formats are re-imported then merged. The final Export for exposure has the Field Ordering option selected as “Cell To Field” which preserves the options from the two previous exports. Make sure to match the resolution, beam step size and any additional machine specific features throughout all the export modules in the flow. The field sizes can be different as long as the final export module has the same or larger field size as the other exports in the flow.

This general technique can be used for other challenging layouts such as mixing overlapping fields and floating fields, multi-pass and floating, plus many more. There is no limit to the number of exports that can be combined into one exposure file. This approach is very useful to improve lithography results by choosing the best strategies and saves time by only exposing one file.